Residual-current circuit breakers are designed and constructed to trip when a residual current of predefined magnitude occurs, and to separate a downstream sub-grid from an upstream power supply grid by opening breaker contacts, thereby protecting persons from dangerous body currents and equipment from fire. However, residual-current circuit breakers, the tripping conditions whereof depend solely on the magnitude or amplitude of an occurring residual current, have the disadvantage that these trip even with very briefly occurring currents greater than a tripping residual current of the pertinent residual-current circuit breaker, which do not constitute a hazard for persons or equipment, whereby downstream technical installations are unnecessarily disconnected. Not only can costs be thereby incurred due to reduced grid availability, but technical processes can also be compromised.
Residual-current circuit breakers with a so-called G-characteristic or F-characteristic provide considerable help with the aforementioned problem. Residual-current circuit breakers of this kind have brief time delays incorporated into their tripping processes, and only trip if the residual current in question exceeds a particular duration. It has been shown, however, that known types of such residual-current circuit breakers nevertheless trip when residual currents amounting to a half-wave in shape and duration, even though such residual current do not present any hazard whatsoever. Thus it still comes down to unnecessary grid disconnections, compromising technical processes and causing repair and maintenance expenses.